The journal "SENSE", volume 8, number 5, Sept./Oct. 82, pages 2/3 discloses a measuring apparatus for use in a wind tunnel which, in addition to measuring the four vertical forces acting upon the wheels of an automobile, by using the distance apart of the axles and the distance apart of the wheels along each axle can measure the tilting and rolling moments (Mx, My). Such known measuring apparatus is manufactured and sold by the assignee of the present invention. The advantage of such an object-related measurement is that the actual wheel forces are measured and that a displacement during the measuring operation does not result in a change in the reading. In this connection it is disadvantageous that the distance apart a.sub.1 of the axles and the distance apart a.sub.2 of the wheels along each axle are not exactly defined in view of the area of the tire surface contacting the supporting surface and variations in manufacture.
In particular, it may happen that the actual force introduction point below each wheel does not correspond with the position of the force transmission member for transmitting the force to a known force measuring element. Furthermore, forces acting onto the object in an air flow may cause a displacement of the object, which again result in a change of the distance between the actual force introduction point and the positioned force introduction point. Such displacements falsify the readings for the tilting and rolling moments (Mx, My).
Alternatively, an apparatus-related measurement of the moments Mx, My may be performed where in the example of a wind tunnel for automobiles one column each for each of the four wheels are arranged at the corners of a rectangle each column bearing at its upper end a double eccentric arm. The columns are connected to each other by a rigid frame. For determining the tilting and rolling moments Mx, My as a moment arm the corresponding distances between two columns b.sub.1 and b.sub.2 are used (see FIG. 1). Hence the influences of a displacement of the force introduction points may be reduced; however, upon application of forces onto the automobile a displacement of the car body in respect of the under frame comprising the motor and the wheels may occur, which displacement results in displacement of the actual centre of gravity in turn resulting in a falsification of the readings of the measurement.